Description
Discovered in the late-1970s, the pioneering drug ivermectin, a dihydro derivative of ivermectin—originating solely from a single microorganism isolated at the Kitasato Institute, Tokyo, Japan from Japanese soil—has had an immeasurably beneficial impact in improving the lives and welfare of billions of people throughout the world. Originally introduced as a veterinary drug, it kills a wide range of internal and external parasites in commercial livestock and companion animals. It was quickly discovered to be ideal in combating two of the world’s most devastating and disfiguring diseases which have plagued the world’s poor throughout the tropics for centuries. It is now being used free-of-charge as the sole tool in campaigns to eliminate both diseases globally.
It has also been used to successfully overcome several other human diseases and new uses for it are continually being found. This paper looks in depth at the events surrounding ivermectin’s passage from being a huge success in Animal Health into its widespread use in humans, a development which has led many to describe it as a “wonder” drug.
Keywords:ivermectin, mode of action, onchocerciasis, lymphatic filariasis, drug resistance
Ivermectin proved to be even more of a ‘Wonder drug’ in human health, improving the nutrition, general health and wellbeing of billions of people worldwide ever since it was first used to treat Onchocerciasis in humans in 1988. It proved ideal in many ways, being highly effective and broad-spectrum, safe, well tolerated and could be easily administered (a single, annual oral dose). It is used to treat a variety of internal nematode infections, including Onchocerciasis, Strongyloidiasis, Ascariasis, cutaneous larva migrants, filariases, Gnathostomiasis and Trichiniasis, as well as for oral treatment of ectoparasitic infections, such as Pediculosis (lice infestation) and scabies (mite infestation).14) Ivermectin is the essential mainstay of two global disease elimination campaigns that should soon rid the world of two of its most disfiguring and devastating diseases, Onchocerciasis and Lymphatic filariasis, which blight the lives of billions of the poor and disadvantaged throughout the tropics. It is likely that, throughout the next decade, well over 200 million people will be taking the drug annually or semi-annually, via innovative globally-coordinated Mass Drug Administration (MDA) programmes. Indeed, the discovery, development and deployment of ivermectin, produced by an unprecedented partnership between the Private Sector pharmaceutical multinational Merck & Co. Inc., and the Public Sector Kitasato Institute in Tokyo, aided by an extraordinary coalition of multidisciplinary international partners and disease-affected communities, has been recognized by many experts and observers as one of the greatest medical accomplishments of the 20th century.15) In referring to the international efforts to tackle Onchocerciasis in which ivermectin is now the sole control tool, the UNESCO World Science Report concluded, “the progress that has been made in combating the disease represents one of the most triumphant public health campaigns ever waged in the developing world”.16)
The origins of ivermectin as a human drug are inextricably linked with Onchocerciasis (or River Blindness), a chronic human filarial disease caused by infection with Onchocerca volvulus worms. The parasites are transmitted via the bite of infected blackflies of the genus Simulium, which breed in highly-oxygenated, fast-flowing rivers and watercourses. In the human body, immature larval forms of the parasite create nodules in subcutaneous tissue, where they mature into adult worms. After mating, female worms can release up to 1000 microfilariae a day for some 10–14 years. These move through the body, and when they die they cause a variety of conditions, including skin rashes, lesions, intense itching, oedema and skin depigmentation (Fig. 2 ). Microfilariae also invade the eye, causing visual impairment and loss of vision, onchocerciasis being the second leading cause of blindness caused by an infectious disease.17) The disease causes visual damage for some 1–2 million people, around half of who will become blind.18)







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